gauges will be calibrated by skilled workers and used by semi-skilled workers; the snap gauge is faster than a micrometer and requires less skill to use correctly. Some vendors who resell a different measuring instrument, bore gauge, muddy the waters by referring to them as snap gauges, unlike the manufacturer who uses the correct nomenclature. Unlike a snap gauge, these measure inside (bore) dimensions, not outside dimensions, and are usually reset for each part measured. References Length, distance, or range measuring devices Metalworking measuring instruments